scholarly journals An analysis of atmospheric CH<sub>4</sub> concentrations from 1984 to 2008 with a single box atmospheric chemistry model

2012 ◽  
Vol 12 (11) ◽  
pp. 30259-30282 ◽  
Author(s):  
Z. Tan ◽  
Q. Zhuang
Keyword(s):  
Growth Rate ◽  
Atmospheric Chemistry ◽  
Methane Flux ◽  
Methane Emissions ◽  
Atmospheric Methane ◽  
Significant Drop ◽  
Oxidizing Power ◽  
The Mean

Abstract. We present a single box atmospheric chemistry model involving atmospheric methane (CH4), carbon monoxide (CO) and radical hydroxyl (OH) to analyze atmospheric CH4 concentrations from 1984 to 2008. When OH is allowed to vary, the modeled CH4 is 20 ppb higher than observations from the NOAA/ESRL and AGAGE networks for the end of 2008. However, when the OH concentration is held constant at 106 molecule cm−3, the simulated CH4 shows a trend approximately equal to observations. Both simulations show a clear slowdown in the CH4 growth rate during recent decades, from about 13 ppb yr−1 in 1984 to less than 5 ppb yr−1 in 2003. Furthermore, if the constant OH assumption is credible, we think that this slowdown is mainly due to a pause in the growth of wetland methane emissions. In simulations run for the Northern and Southern Hemispheres separately, we find that the Northern Hemisphere is more sensitive to wetland emissions, whereas the southern tends to be more perturbed by CH4 transportation, dramatic OH change, and biomass burning. When measured CO values from NOAA/ESRL are used to drive the model, changes in the CH4 growth rate become more consistent with observations, but the long-term increase in CH4 is underestimated. This shows that CO is a good indicator of short-term variations in oxidizing power in the atmosphere. The simulation results also indicate the significant drop in OH concentrations in 1998 (about 5% lower than the previous year) was probably due to an abrupt increase in wetland methane emissions during an intense EI Niño event. Using a fixed-lag Kalman smoother, we estimate the mean wetland methane flux is about 128 Tg yr−1 through the period 1984–2008. This study demonstrates the effectiveness in examining the role of OH and CO in affecting CH4.

Long-term dynamics and destruction of marsh vegetation in the Kolokolkova Bay of the Barents Sea

2012 ◽  
pp. 66-77 ◽  
Author(s):  
I. A. Lavrinenko ◽  
O. V. Lavrinenko ◽  
D. V. Dobrynin
Keyword(s):  
Species Composition ◽  
Plant Communities ◽  
Barents Sea ◽  
Mean Value ◽  
Marsh Vegetation ◽  
Composition And Structure ◽  
The Mean ◽  
Species Composition And Structure

The satellite images show that the area of marshes in the Kolokolkova bay was notstable during the period from 1973 up to 2011. Until 2010 it varied from 357 to 636 ha. After a severe storm happened on July 24–25, 2010 the total area of marshes was reduced up to 43–50 ha. The mean value of NDVI for studied marshes, reflecting the green biomass, varied from 0.13 to 0.32 before the storm in 2010, after the storm the NDVI decreased to 0.10, in 2011 — 0.03. A comparative analysis of species composition and structure of plant communities described in 2002 and 2011, allowed to evaluate the vegetation changes of marshes of the different topographic levels. They are fol­lowing: a total destruction of plant communities of the ass. Puccinellietum phryganodis and ass. Caricetum subspathaceae on low and middle marches; increasing role of halophytic species in plant communities of the ass. Caricetum glareosae vic. Calamagrostis deschampsioides subass. typicum on middle marches; some changes in species composition and structure of plant communities of the ass. Caricetum glareosae vic. Calamagrostis deschampsioides subass. festucetosum rubrae on high marches and ass. Parnassio palustris–Salicetum reptantis in transition zone between marches and tundra without changes of their syntaxonomy; a death of moss cover in plant communities of the ass. Caricetum mackenziei var. Warnstorfia exannulata on brackish coastal bogs. The possible reasons of dramatic vegetation dynamics are discussed. The dating of the storm makes it possible to observe the directions and rates of the succession of marches vegetation.

scholarly journals Variability and quasi-decadal changes in the methane budget over the period 2000–2012

2017 ◽  
Author(s):  
Marielle Saunois ◽  
Philippe Bousquet ◽  
Benjamin Poulter ◽  
Anna Peregon ◽  
Philippe Ciais ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Methane Emissions ◽  
Data Driven ◽  
Atmospheric Methane ◽  
Top Down ◽  
Bottom Up ◽  
Ch4 Emissions ◽  
Ensemble Mean ◽  
The Mean ◽  
The Tropics

Abstract. Following the recent Global Carbon project (GCP) synthesis of the decadal methane (CH4) budget over 2000–2012 (Saunois et al., 2016), we analyse here the same dataset with a focus on quasi-decadal and inter-annual variability in CH4 emissions. The GCP dataset integrates results from top-down studies (exploiting atmospheric observations within an atmospheric inverse-modelling frameworks) and bottom-up models, inventories, and data-driven approaches (including process-based models for estimating land surface emissions and atmospheric chemistry, inventories of anthropogenic emissions, and data-driven extrapolations). The annual global methane emissions from top-down studies, which by construction match the observed methane growth rate within their uncertainties, all show an increase in total methane emissions over the period 2000–2012, but this increase is not linear over the 13 years. Despite differences between individual studies, the mean emission anomaly of the top-down ensemble shows no significant trend in total methane emissions over the period 2000–2006, during the plateau of atmospheric methane mole fractions, and also over the period 2008–2012, during the renewed atmospheric methane increase. However, the top-down ensemble mean produces an emission shift between 2006 and 2008, leading to 22 [16–32] Tg CH4 yr−1 higher methane emissions over the period 2008–2012 compared to 2002–2006. This emission increase mostly originated from the tropics with a smaller contribution from mid-latitudes and no significant change from boreal regions. The regional contributions remain uncertain in top-down studies. Tropical South America and South and East Asia seems to contribute the most to the emission increase in the tropics. However, these two regions have only limited atmospheric measurements and remain therefore poorly constrained. The sectorial partitioning of this emission increase between the periods 2002–2006 and 2008–2012 differs from one atmospheric inversion study to another. However, all top-down studies suggest smaller changes in fossil fuel emissions (from oil, gas, and coal industries) compared to the mean of the bottom-up inventories included in this study. This difference is partly driven by a smaller emission change in China from the top-down studies compared to the estimate in the EDGARv4.2 inventory, which should be revised to smaller values in a near future. Though the sectorial partitioning of six individual top-down studies out of eight are not consistent with the observed change in atmospheric 13CH4, the partitioning derived from the ensemble mean is consistent with this isotopic constraint. At the global scale, the top-down ensemble mean suggests that, the dominant contribution to the resumed atmospheric CH4 growth after 2006 comes from microbial sources (more from agriculture and waste sectors than from natural wetlands), with an uncertain but smaller contribution from fossil CH4 emissions. Besides, a decrease in biomass burning emissions (in agreement with the biomass burning emission databases) makes the balance of sources consistent with atmospheric 13CH4 observations. The methane loss (in particular through OH oxidation) has not been investigated in detail in this study, although it may play a significant role in the recent atmospheric methane changes.

scholarly journals Development of Algorithm for Clinical Management of Sickle Cell Bone Disease: Evidence for a Role of Vertebral Fractures in Patient Follow-up

2020 ◽  
Vol 9 (5) ◽  
pp. 1601 ◽  
Author(s):  
Lucia De Franceschi ◽  
Daniele Gabbiani ◽  
Andrea Giusti ◽  
Gianluca Forni ◽  
Filippo Stefanoni ◽  
...  
Keyword(s):  
Bone Density ◽  
Sickle Cell ◽  
Bone Disease ◽  
Vertebral Fractures ◽  
Cell Disease ◽  
High Incidence ◽  
The Mean

Sickle-cell disease (SCD) is a worldwide distributed hemoglobinopathy, characterized by hemolytic anemia associated with vaso-occlusive events. These result in acute and chronic multiorgan damage. Bone is early involved, leading to long-term disability, chronic pain and fractures. Here, we carried out a retrospective study to evaluate sickle bone disease (SBD) in a cohort of adults with SCD. We assessed bone density, metabolism and turnover. We also evaluated the presence of fractures and the correlation between SCD severity and skeletal manifestations. A total of 71 patients with SCD were analyzed. The mean age of population was 39 ± 10 years, 56% of which were females. We found osteoporosis in a range between 7% and 18% with a high incidence of vertebral fractures. LDH and AST were predictive for the severity of vertebral fractures, while bone density was not. Noteworthy, we identified -1.4 Standard Deviations T-score as the cutoff for detecting the presence of fractures in patients with SCD. Collectively our data allowed us to develop an algorithm for the management of SBD, which may be useful in daily clinical practice to early intersect and treat SBD.

Air Chemistry

1959 ◽  
Vol 40 (10) ◽  
pp. 493-498 ◽  
Author(s):  
Christian E. Junge
Keyword(s):  
Atmospheric Chemistry ◽  
Aerosol Particles ◽  
Trace Gases ◽  
Special Importance ◽  
Physical Processes ◽  
Industrial Activities ◽  
Cent Increase ◽  
Air Chemistry

The field of atmospheric chemistry, which is defined as the chemistry of trace substances in the troposphere, is reviewed. Trace substances can be present as aerosols or as gases. Major sources of aerosols are the ocean and industrial activities. The chemical composition of the aerosol particles is not only determined by their source but also by various processes in the atmosphere—notably, reactions with gas traces. Only little is known about trace gases like SO2, H2S, NH3 or NO2. Of special importance for meteorology is CO2 and its long-term fluctuations. The facts and possible reasons for its 10 per cent increase during this century are discussed. The last part of the discussion is concerned with the physical processes by which the trace substances are removed from the atmosphere, primarily the role of precipitation.

Comparative performance of cattle and buffalo on the Sepik Plains, Papua New Guinea

1977 ◽  
Vol 17 (87) ◽  
pp. 550 ◽  
Author(s):  
JH Schottler ◽  
A Boromana ◽  
WT Williams
Keyword(s):  
Growth Rate ◽  
Papua New Guinea ◽  
Water Buffalo ◽  
New Guinea ◽  
Comparative Performance ◽  
Mineral Supplementation ◽  
Calf Mortality ◽  
The Mean ◽  
Native Pastures

Fifty female Brahman-cross cattle and 50 water buffalo were run on the infertile native pastures of the Sepik lowland plains, Papua New Guinea; half the buffalo, and all the cattle, received mineral supplementation (phosphate, Ca, Cu and Co). After the beginning of the experiment all animals were able to maintain, but not improve, their weights. The liveweights attained were everywhere less than those attained on more fertile pastures elsewhere in Papua New Guinea, the discrepancy being greater for cattle than for buffalo. Supplementation improved both the mean liveweight of buffalo and the growth rate of the calves. Calf mortality was 18 per cent in both species. Despite the longer gestation period, the buffalo produced nearly 50 per cent more calves than the cattle; buffalo more often than not conceived while still lactating, whereas cattle did so only rarely. There was some evidence of a long-term improvement in fertility as a result of supplementation. It is concluded that under these difficult conditions buffalo are a better proposition than cattle.

THE PROFILE OF MULTIPLE SCLEROSIS IN GENERAL PRACTICE

2015 ◽  
Vol 86 (11) ◽  
pp. e4.6-e4
Author(s):  
Sophie Binks ◽  
Liz Green
Keyword(s):  
Multiple Sclerosis ◽  
Primary Care ◽  
Team Approach ◽  
Improvement Project ◽  
Flu Vaccination ◽  
The Mean ◽  
One Year ◽  
Primary Care Professionals

IntroductionMultiple sclerosis (MS) is a long-term neurological condition requiring a multi-disciplinary team approach. Recently, NICE highlighted the role of primary care professionals in MS management through an updated clinical guideline. This quality improvement project investigated aspects of MS patient care in a large Brighton GP practice.MethodElectronic GP records were searched to identify all currently registered patients with a diagnosis of MS. Details of initial presentation, epidemiology and care received over a one-year period were examined.ResultsThere were 19 patients, representing a prevalence of 186 per 100,000. Most patients first presented in GP with sensory disturbance, optic neuritis or motor symptoms. The mean number of primary care contacts per patient per year was 4.3, compared to 0.4 contacts per person per year with a neurologist and 0.5 with the MS nurse. 46% of GP consultations were wholly or partially related to the patient's MS. Around half of patients took up proactive interventions such as flu vaccination (47%) and Vitamin D monitoring (50%).ConclusionsPrimary care professionals are significant contributors to the care of people with MS with frequent patient contact. During this project, patients were reminded of preventive care opportunities and this will be re-audited in 2015.

scholarly journals Measuring the Effect of the Internet on Economic Growth: The Case of Saudi Arabia

2020 ◽  
Vol 12 (12) ◽  
pp. 61
Author(s):  
Hisham J. Bardesi
Keyword(s):  
Economic Growth ◽  
Growth Rate ◽  
Saudi Arabia ◽  
Internet Access ◽  
Ordinary Least Squares ◽  
The Internet ◽  
Macroeconomic Performance ◽  
The Impact

The purpose of this study is to examine and assess the impact of the Internet on economic growth in Saudi Arabia. Various studies show that there is a relationship between the growth rate of GDP and the Internet, as estimated by Internet user numbers. In this paper, the ordinary least squares (OLS) model is utilized to study the economic impact of Internet Access from 1994 to 2018, which has had a profound effect on the market structure of many sectors and Saudi&rsquo;s global macroeconomic performance. The study constructs a model to investigate any significant impact of the Internet on the Saudi economy. Finally, this paper suggests that an understanding of the role of the Internet is essential for policymakers who plan to promote new forms of economic growth in the future. To take a long-term view implies working on technologies that could improve the economy and people&rsquo;s lives by creating a technological ecosystem in and around Saudi Arabia, along with other major economies.

scholarly journals COVID-19 lockdown NO<sub>x</sub> emission reductions can explain most of the coincident increase in global atmospheric methane

2021 ◽  
Author(s):  
David Stevenson ◽  
Richard Derwent ◽  
Oliver Wild ◽  
William Collins
Keyword(s):  
Growth Rate ◽  
Atmospheric Chemistry ◽  
Global Scale ◽  
Chemical System ◽  
Nox Emissions ◽  
Atmospheric Methane ◽  
Emission Reductions ◽  
Great Utility ◽  
Key Factor ◽  
Global Growth

Abstract. Compared to 2019, the global growth rate of atmospheric methane rose by about 50 % in 2020, reaching 15 ppb/yr. Models of global atmospheric chemistry show that reductions in nitrogen oxide (NOx) emissions reduce levels of the hydroxyl radical, and lengthen the methane lifetime. Using estimates of NOx emission reductions associated with COVID-19 lockdowns around the world in 2020, together with model-derived regional and sectoral sensitivities of methane to NOx emissions, we find that NOx emissions reductions can fully explain the observed surge in the global methane growth rate. Whilst changes in NOx emissions are probably not the only important factor that has influenced methane since the beginning of 2020, it is clear that they are a key factor that will need to be included within any attribution study, and that they may well be the dominant driver of these recent methane changes. The major global scale changes in composition of the Earth’s atmosphere measured during lockdown provide unprecedented constraints on the sensitivity of the atmospheric chemical system to changes in emissions, and are of great utility for evaluating policy-relevant models.

scholarly journals Can we explain the observed methane variability after the Mount Pinatubo eruption?

2015 ◽  
Vol 15 (13) ◽  
pp. 19111-19160
Author(s):  
N. Bândă ◽  
M. Krol ◽  
M. van Weele ◽  
T. van Noije ◽  
P. Le Sager ◽  
...  
Keyword(s):  
Growth Rate ◽  
Biomass Burning ◽  
Partial Recovery ◽  
Mount Pinatubo ◽  
Sources And Sinks ◽  
Time Period ◽  
Pinatubo Eruption ◽  
Emission Changes

Abstract. The CH4 growth rate in the atmosphere showed large variations after the Pinatubo eruption in June 1991. A decrease of more than 10 ppb yr-1 in the growth rate over the course of 1992 was reported and a partial recovery in the following year. Although several reasons have been proposed to explain the evolution of CH4 after the eruption, their contributions to the observed variations are not yet resolved. CH4 is removed from the atmosphere by the reaction with tropospheric OH, which in turn is produced by O3 photolysis under UV radiation. The CH4 removal after the Pinatubo eruption might have been affected by changes in tropospheric UV levels due to the presence of stratospheric SO2 and sulfate aerosols, and due to enhanced ozone depletion on Pinatubo aerosols. The perturbed climate after the eruption also altered both sources and sinks of atmospheric CH4. Furthermore, CH4 concentrations were influenced by other factors of natural variability in that period, such as ENSO and biomass burning events. Emissions of CO, NOX and NMVOCs also affected CH4 concentrations indirectly by influencing tropospheric OH levels. Potential drivers of CH4 variability are investigated using the TM5 global chemistry model. The contribution that each driver had to the global CH4 variability during the period 1990 to 1995 is quantified. We find that a decrease of 8–10 ppb yr-1 CH4 is explained by a combination of the above processes. However, the timing of the minimum growth rate is found 6–9 months later than observed. The long-term decrease in CH4 growth rate over the period 1990 to 1995 is well captured and can be attributed to an increase in OH concentrations over this time period. Potential uncertainties in our modelled CH4 growth rate include emissions of CH4 from wetlands, biomass burning emissions of CH4 and other compounds, biogenic NMVOC and the sensitivity of OH to NMVOC emission changes. Two inventories are used for CH4 emissions from wetlands, ORCHIDEE and LPJ, to investigate the role of uncertainties in these emissions. Although the higher climate sensitivity of ORCHIDEE improves the simulated CH4 growth rate change after Pinatubo, none of the two inventories properly captures the observed CH4 variability in this period.

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